Background: Estrogen and progesterone receptor assays (ER and PgR), thymidine labeling index (TLI), DNA flow cytometric measurements of DNA index (DNAI) and S-phase fraction (SPF), and in vitro clonogenic testing of drug sensitivity have been applied to breast carcinomas. Preliminary studies in our laboratory indicate that some breast carcinomas have different DNAIs in different geographic locations or intermingled in some locations, indicative of multiple stemlines. Therefore, any of the above studies performed on a single sample may not be representative of the entire tumor. Specific Aims: Geographic characterization of 50 primary breast carinomas for DNAI, TLI, ER, PgR. The objectives are to determine: 1. The frequency of heterogeneity of the DNAI for high vs. low mean ER, mean PgR and mean TLI. 2. Whether samples with different DNAI have characteristically different levels of ER, PgR and TLI. 3. Whether heterogeneity can be predicted by TLI, SPF, ER, PgR, age of patient, size or histologic characteristics of the tumor. 4. Whether the DNAI influences propensity for axillary metastasis. 5. Establish correlations of image analysis with DNAI, SPF and TLI. Methodology: The neoplasm will be dissected from the breast and sampled systematically, and each axillary metastasis will be sampled. The number of samples for flow cytometry will vary from 3 for carcinomas with 1.5 cm diameter to 33 for 10 cm diameter with fewer samples for TLI and receptor assays. The specimens for flow cytometry will be cryopreserved for subsequent propidium iodide staining and flow microfluorimetry at 488 nm excitation. Fresh tissue slices will be incubated with tritiated thymidine in presence of 2'-deoxy-5-fluorouracil and hyperbaric oxygen prior to fixation, sectioning and autoradiography. Receptor assays will be done on cytosol by Scatchard plot with correction for nonspecific binding and isoform analysis by chromatography. Microscopic image analysis will be done by digital computer analysis. Data will be analyzed by computer using standard programs and statistical methods. Long-Term Objectives: 1. Improve evaluation of breast carcinoma patients by optimizing tumor sampling for various assays. 2. Provide basis for studies of relationships between tumor heterogeneity and sensitivity to hormones, cytotoxic agents and radiation.